ci(config.yml): add black formatting to ci/cd pipeline

.circleci/config.yml

@@ -43,6 +43,13 @@ jobs:
           paths:
             - ./venv
           key: v1-dependencies-{{ checksum ".circleci/requirements.txt" }}
+      - run:
+          name: Black Formatting
+          command: |
+            cd litellm
+            python -m pip install black
+            python -m black .
+            cd ..
       - run:
           name: Linting Testing
           command: |